Data Sheet 1_Role of methanotrophic communities in atmospheric methane oxidation in paddy soils.docx

Wetland systems are known methane (CH4) sources. However, flooded rice fields are periodically drained. The paddy soils can absorb atmospheric CH4 during the dry seasons due to high-affinity methane-oxidizing bacteria (methanotroph). Atmospheric CH4 uptake can be induced during the low-affinity oxidation of high-concentration CH4 in paddy soils. Multiple interacting factors control atmospheric CH4 uptake in soil ecosystems. Broader biogeographical data are required to refine our understanding of the biotic and abiotic factors related to atmospheric CH4 uptake in paddy soils. Thus, here, we aimed to assess the high-affinity CH4 oxidation activity and explored the community composition of active atmospheric methanotrophs in nine geographically distinct Chinese paddy soils. Our findings demonstrated that high-affinity oxidation of 1.86 parts per million by volume (ppmv) CH4 was quickly induced after 10,000 ppmv high-concentration CH4 consumption by conventional methanotrophs. The ratios of 16S rRNA to rRNA genes (rDNA) for type II methanotrophs were higher than those for type I methanotrophs in all acid-neutral soils (excluding the alkaline soil) with high-affinity CH4 oxidation activity. Both the 16S rRNA:rDNA ratios of type II methanotrophs and the abundance of 13C-labeled type II methanotrophs positively correlated with high-affinity CH4 oxidation activity. Soil abiotic factors can regulate methanotrophic community composition and atmospheric CH4 uptake in paddy soils. High-affinity methane oxidation activity, as well as the abundance of type II methanotroph, negatively correlated with soil pH, while they positively correlated with soil nutrient availability (soil organic carbon, total nitrogen, and ammonium-nitrogen). Our results indicate the importance of type II methanotrophs and abiotic factors in atmospheric CH4 uptake in paddy soils. Our findings offer a broader biogeographical perspective on atmospheric CH4 uptake in paddy soils. This provides evidence that periodically drained paddy fields can serve as the dry-season CH4 sink. This study is anticipated to help in determining and devising greenhouse gas mitigation strategies through effective farm management in paddy fields.

湿地系统被认为是甲烷（CH4）的来源。然而，水田在周期性排水。由于具有高亲和力甲烷氧化菌（甲烷营养菌），水田土壤在干燥季节能够吸收大气中的CH4。在大浓度CH4的低亲和力氧化过程中，可以诱导大气CH4的吸收。多种相互作用的因素控制着土壤生态系统中大气CH4的吸收。为了深化我们对与水田土壤中大气CH4吸收相关的生物和非生物因素的理解，需要更广泛的生物地理数据。因此，本研究旨在评估高亲和力CH4氧化活性，并探讨九个地理上独特的中国水田土壤中活性大气甲烷营养菌的群落组成。我们的研究结果表明，在传统甲烷营养菌消耗10,000 ppmv高浓度CH4后，1.86 ppmv CH4的高亲和力氧化迅速被诱导。在所有具有高亲和力CH4氧化活性的酸中性土壤（不包括碱性土壤）中，II型甲烷营养菌的16S rRNA与rRNA基因（rDNA）的比率高于I型甲烷营养菌。II型甲烷营养菌的16S rRNA:rDNA比率以及13C标记的II型甲烷营养菌的丰度与高亲和力CH4氧化活性呈正相关。土壤的非生物因素可以调节甲烷营养菌群落组成和水田土壤中大气CH4的吸收。高亲和力甲烷氧化活性以及II型甲烷营养菌的丰度与土壤pH呈负相关，而与土壤养分可用性（土壤有机碳、总氮和铵态氮）呈正相关。我们的研究结果指出，II型甲烷营养菌和非生物因素在土壤中大气CH4吸收中的重要性。我们的发现为水田土壤中大气CH4吸收提供了更广泛的生物地理视角。这为周期性排水的稻田可以作为干燥季节的CH4汇提供了证据。本研究有望帮助确定和制定通过有效的水田农场管理减少温室气体排放的策略。